An acoustic transducer is generally formed of a plurality of stacks of planar piezoelectric crystals mounted in spaced parallel overlapping relationship. Electrical leads respectively in contact with one side of the crystals are used to apply electrical signals to the crystals so as to cause them to transmit acoustic energy and to conduct the electrical signals generated by the crystals in response to their reception of acoustic energy.
It is possible to bond each lead to a different crystal, but the dimensions are generally so small that this is tedious and expensive and runs the risk of short circuits between crystals.
In a U.S. Pat. No. 4,404,489, "Method and Means for Producing an Acoustic Transducer", filed on Nov. 3, 1980, the names of John D. Larson III and David George Miller and assigned to Hewlett-Packard Company, as is this application, a technique for attaching the leads is described wherein a flexible circuit board having the leads adhered thereto is mounted with the leads aligned with the individual crystals and bonded thereto. One of the problems with this structure is the fact that the circuit board material is in the path of the acoustic waves being transmitted and received and has such acoustic properties as to reduce the effectiveness of the transducer.